Using R to Orchestrate APIs

A presentation for Research Data at the Edge, Day One of Duke Research Computing Symposium

Hosted by the Data & Visualization Services Department.

Presentation materials composed in Rmarkdown using Rstudio, stored in a Github Repository, Served via Github Pages.

Outline

Why?

The Web has lots of stuff

  • frontier beyond curated datasets
  • stuff is wrapped in HTML
  • HTML is transported over HTTP but composed for h2m consumption
  • Intellectual Property rights bear serious consideration

API

Application Program Interface

  • Built for machine-to-machine interactions
  • Instructions for programs

Client / Server

  • Make [R] interface with the web
  • Same as h2m but now m2m

Human Simulation

A dramatization…

  • Person uses Web Client
    • Person enters a URL

    • client & server negotiate
      dramatization: good handshake
    • Information is sent back in wrapped HTML
    • Web Browser parses the HTML

m2m – development

dramatization: confused about the protocol

dramatization: confused about the protocol

JSON

# from https://en.wikipedia.org/wiki/JSON
{
  "firstName": "John",
  "lastName": "Smith",
  "isAlive": true,
  "age": 25,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021-3100"
  },
  "phoneNumbers": [
    {
      "type": "home",
      "number": "212 555-1234"
    },
    {
      "type": "office",
      "number": "646 555-4567"
    },
    {
      "type": "mobile",
      "number": "123 456-7890"
    }
  ],
  "children": [],
  "spouse": null
}

Example

Demonstration

library(jsonlite)
# https://cran.r-project.org/web/packages/jsonlite/vignettes/json-aaquickstart.html
# for building tibbles
library(tidyverse)

Single JSON array

When the server response is a single JSON array, JSONlite makes viewing the data pretty simple.

oneJSONresult <- fromJSON("http://www.omdbapi.com/?t=rocky&y=&plot=full&r=json")
# oneJSONresult

Let’s see the results in the next slide


oneJSONresult
$Title
[1] "Rocky"

$Year
[1] "1976"

$Rated
[1] "PG"

$Released
[1] "03 Dec 1976"

$Runtime
[1] "120 min"

$Genre
[1] "Drama, Sport"

$Director
[1] "John G. Avildsen"

$Writer
[1] "Sylvester Stallone"

$Actors
[1] "Sylvester Stallone, Talia Shire, Burt Young, Carl Weathers"

$Plot
[1] "Rocky Balboa is a struggling boxer trying to make the big time, working as a debt collector for a pittance. When heavyweight champion Apollo Creed visits Philadelphia, his managers want to set up an exhibition match between Creed and a struggling boxer, touting the fight as a chance for a \"nobody\" to become a \"somebody\". The match is supposed to be easily won by Creed, but someone forgot to tell Rocky, who sees this as his only shot at the big time."

$Language
[1] "English"

$Country
[1] "USA"

$Awards
[1] "Won 3 Oscars. Another 16 wins & 21 nominations."

$Poster
[1] "https://images-na.ssl-images-amazon.com/images/M/MV5BMTY5MDMzODUyOF5BMl5BanBnXkFtZTcwMTQ3NTMyNA@@._V1_SX300.jpg"

$Metascore
[1] "N/A"

$imdbRating
[1] "8.1"

$imdbVotes
[1] "387,927"

$imdbID
[1] "tt0075148"

$Type
[1] "movie"

$Response
[1] "True"

The vector object behaves as you would expect in R.
  • You can list all the variable names.
names(oneJSONresult)
 [1] "Title"      "Year"       "Rated"      "Released"   "Runtime"    "Genre"      "Director"   "Writer"     "Actors"    
[10] "Plot"       "Language"   "Country"    "Awards"     "Poster"     "Metascore"  "imdbRating" "imdbVotes"  "imdbID"    
[19] "Type"       "Response"  
  • List an individual element
oneJSONresult$Title
[1] "Rocky"
oneJSONresult$Awards

A JSON Matrix

The results of this code-snippet react differently between the console, the Notebook script (console), and the Notebook HTML output. In the Notebook script-output you can find the component name, in this case dollar-search: $Search. Or, you can use bracket notation: [[1]]. Once you identify the component name, it’s easier to identify the element names.

jsonSeriesResutlsMatrix <- fromJSON("http://www.omdbapi.com/?s=rocky&type=series&r=json&page=1")
jsonSeriesResutlsMatrix
$Search

$totalResults
[1] "20"

$Response
[1] "True"

Call the search results and coerce the JSON array into a data frame.

jsonSeriesResutlsMatrix$Search

jsonSeriesResutlsMatrix$Search$Title

Resources

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